Abstract
BackgroundHuman endogenous retroviruses (HERVs) comprise approximately 8% of the human genome and while the majority are transcriptionally silent, the most recently integrated HERV, HERV-K (HML-2), remains active. During HIV infection, HERV-K (HML-2) specific mRNA transcripts and viral proteins can be detected. In this study, we aimed to understand the antibody response against HERV-K (HML-2) Gag in the context of HIV-1 infection.ResultsWe developed an ELISA assay using either recombinant protein or 164 redundant “15mer” HERV-K (HML-2) Gag peptides to test sera for antibody reactivity. We identified a total of eight potential HERV-K (HML-2) Gag immunogenic domains: two on the matrix (peptides 16 and 31), one on p15 (peptide 85), three on the capsid (peptides 81, 97 and 117), one on the nucleocapsid (peptide 137) and one on the QP1 protein (peptide 157). Four epitopes (peptides 16, 31, 85 and 137) were highly immunogenic. No significant differences in antibody responses were found between HIV infected participants (n = 40) and uninfected donors (n = 40) for 6 out of the 8 epitopes tested. The antibody response against nucleocapsid (peptide 137) was significantly lower (p < 0.001), and the response to QP1 (peptide 157) significantly higher (p < 0.05) in HIV-infected adults compared to uninfected individuals. Among those with HIV infection, the level of response against p15 protein (peptide 85) was significantly lower in untreated individuals controlling HIV (“elite” controllers) compared to untreated non-controllers (p < 0.05) and uninfected donors (p < 0.05). In contrast, the response against the capsid protein (epitopes 81 and 117) was significantly higher in controllers compared to uninfected donors (p < 0.001 and <0.05 respectively) and non-controllers (p < 0.01 and <0.05). Peripheral blood mononuclear cells (PBMCs) from study participants were tested for responses against HERV-K (HML-2) capsid recombinant peptide in gamma interferon (IFN-γ) enzyme immunospot (Elispot) assays. We found that the HERV-K (HML-2) Gag antibody and T cell response by Elispot were significantly correlated.ConclusionsHIV elite controllers had a strong cellular and antibody response against HERV-K (HML-2) Gag directed mainly against the Capsid region. Collectively, these data suggest that anti-HERV-K (HML-2) antibodies targeting capsid could have an immunoprotective effect in HIV infection.
Highlights
Human endogenous retroviruses (HERVs) comprise approximately 8% of the human genome and while the majority are transcriptionally silent, the most recently integrated HERV, HERV-K (HML-2), remains active
We showed that strong anti-HERV-K (HML-2) capsid response is more frequently found in elite controllers (ECs) compared to viremic non-controllers (VNCs) and HIV-negative low risk donors (SNLR)
The anti‐HERV‐K (HML‐2) Capsid response correlates with anti‐HERV Gag T‐cell response in elite controllers We first evaluated the antibody response against HERVK (HML-2) recombinant capsid protein in uninfected donors and in untreated HIV-infected participants who were categorized as ECs or VNCs (Fig. 1)
Summary
Human endogenous retroviruses (HERVs) comprise approximately 8% of the human genome and while the majority are transcriptionally silent, the most recently integrated HERV, HERV-K (HML-2), remains active. We aimed to understand the antibody response against HERV-K (HML-2) Gag in the context of HIV-1 infection. Human endogenous retroviruses (HERVs) are fossil remnants of inherited retroviruses which were endogenized into the genome, and comprise about 5–8% of the human genome [1]. The mechanisms leading to HERV-K (HML-2) expression are still being elucidated, but HIV Vif and Tat proteins have been implicated [27, 29]. It appears that the transactivation of HERV-K by exogenous HIV is more complex than initial studies suggested. We showed that isolated HERV-K specific T-cell clones and HA137, a human anti-HERV-K (HML-2) TM antibody, eliminated HIV infected cells in vitro [26,27,28, 30, 31]
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